Process for improving the surface of form ground races



Feb. 1, 1949. SEYFERTH 2,460,472

7 PROCESS FOR IMPROVING THE SURFACE OF FORM GROUND RACES Filed Oct. 13, 1945 3 Sheets-Sheet l INVEN TOR. Haw/.0 A/ 5EYFER7'H.

Feb. 1, 1949. SEYFERTH 2,460,472

PROCESS FOR IMPROV THE SURFACE OF FORM GRO RACES Filed 001;. 15, 1943 3 Sheets-Sheet 2 v INVENTOR.

HAROLD A/ SEYFERTH Feb. 1, 1949. EY 2,460,472

PROCESS FOR IMPROVING THE SURFACE OF FORM GROUND RACES. Filed Oct. 13, 1943 3 Sheets-Sheet 3 INVENTOR. B Hfl/FOLD/V SEYFERTH fl TTOENE Y .in short curved lines instead of in points.

Patented Feb. 1, 1949 PROCESS FOR IMPROVING THE SURFACE OF FORM GROUND RACES Harold N. Seyferth, East Detroit, Mich., assignor to Ex-Cell-O Corporation, Detroit, Mich a corporation of Michigan Application October 13, 1943, Serial No. 506,046

This invention relates generally to the manufacture of ball bearings. It has particular reference to an improved process for preparing the ball contacted raceway surfaces to be finished by the method of finishing ball bearings patented to Carroll R. Alden, April 9, 1929, in United States Patent No. 1,708,491.

An object of the invention is to improve the smoothness of operation and increase the useful lifeof ball bearings.

Usually the preparation of the races of such bearings has included the. step of bringing the ball contacted race surfaces to the desired form by rotating them in cutting contact with a rotating, suitably formed grinding Wheel in a manner which generates on the race a complementarily formed surface of revolution. And the step just described has been the step which immediately precedes the application of the said Alden method of finishing ball bearings.

Form ground race surfaces so prepared characteristically contain periodically recurring protuberant aberrations from the theoretically perfect contour of the generated circular sections taken in planes normal to the axis of rotation. These aberrations are known as chatter. The degree Ofchatter may relate to unavoidablelooseness in the spindle bearings or, the workhead bearings or both, which are incorporated in the machine in which the surfaces are ground, or to other unavoidable machine conditions. The protuberant aberrations are found to be generally parallel to the line of contact between the generated surface and the generating abrasive wheel durin the generating operation.

In the form grinding step, as last described, the axes of revolution of race and abrasive wheel are preferably maintained co-planar and parallel, with the result that the protuberant aberrations last described appear in the plane containing the said axes and aremade manifest as waves superimposed upon circular cross sections through the race. They, therefore, have their lengths in planes which include the axis of the race.

These aberrations in .well ground work may appear to be .very slight under ordinary visual observation, nevertheless, any aberrations, however slight, 'have a deleterious effect upon the smoothness and length of life of bearings containing such errors. If excessive, such aberrations may not be entirely removed by the Alden patented method of finishing, which has as an important object the wearing in of a ball race track permitting the balls to contact the races (See 4 Claims. (Cl. 51-29'1) particularly page 2, lines 55-70, United States Patent No. 1,708,491.) The results of the Alden method will more closely approach the desired condition of perfect fitting between balls and races if the raceway surfaces are prepared with geometrical precision prior to the step of performing the patented finishing method. When the races are properly prepared for finishing by the Alden method, the wearing in of balls and races, which is performed therein, need be relied upon only to increase the contact between balls and races to the desired extent and to develop with accuracy that adjusted relation between the parts thereof which will enable the bearing to operate at high speeds without damage to its parts.

In the drawings, I

Fig. 1 is an axial section through a bearing to which the present process may advantageously be applied.

Fig. 2 is an elevation of a fragmentary portion of the inner race of the bearing of Fig. 1 shown in form grindin relation with a grinding Wheel of complementary'shape.

Fig. 3 is a transverse cross section on lines 3-3 of Fig. 2 showing protuberant aberrations trans- ,versely of their principal lengths and greatly magnified for illustrative purposes.

Fig. 4 shows an elevation of a fragmentary portion of the inner race and a pattern wheel in pattern forming relation thereto and shows the relation of an abrasive wheel in a subsequent corrective abrading step to the race member to 7 be corrected thereby.

Fig. 5 is a view similar to Fig. 4 but shows the relationships of wheel and race in an additional pattern'forming and corrective step.

Fig. 6 is a view showing a fragmentary portion of the surface of the race of Fig. 2, developed for depiction in the plane of the paper, after having had performed thereupon the corrective steps illustrated in Figs. 4 and 5.

Referring now to the drawing and particularly to Fig. 1, the bearing assembly is shown having an inner race member 2 provided with grooves 3 for the reception of the balls 4. A ball spacing retainer 8 is pocketed to space the balls 4. The inner ends of the pockets are of slightly reduced diameter to prevent passage of the balls 4 therethrough on removal of the retainer assembly from its assembled relation to the inner race. A closed coiled springlike contractible member In snapped into its receivin groove II is provided for the purpose of retaining the balls 4 from outward exit upon removal of outer races 6.

The race grooves 3 which are contacted by the balls 4 at points A and B of Fig. 1 are shown in Fig. 2 in form generating relationship with a grinding wheel 12 having an axial cutting periphery i lwhich is complementary in shape to the axial cross section through the race groove form 3. In the illustrative instance, the axes of rotation of wheel i2 and race 2 are co-planar and parallel in the plane Al-Al. Any protuberant aberrations are generated along the line i5i5 which is also in the plane All-PAL These appear in the elevation as a multiplicity of protuberances iii and are shown in exaggerated transverse cross section in Fig. 3.

The protuberances i6 are reduced or removed, according to the present process, by performing a corrective lapping or fine abrading step which regenerates the axial cross section of the race shown in Figs. 1 and 2 without substantial alteration of the dimensions thereof. This is done in a correcting abrading operation generally similar tothat shown in'Fig. {l in which theaxis of race-2 is rotated in the reference plane A1A1.

lapping wheel [3 is rotated in plane A2A2 which like Ai-Ai is perpendicular to the plane of the paper but makes. with plane ill-9A1, the angle a. Lapping wheel it" has acutting periphery I81 which is formed tocontact'the axial cross section of the ball contacted surfacesfi of race 2 in a curved line 2 2Q in such manner that the radial cutting pressure exerted between lapping wheel l8 and racefl (by'any convenient machine means not shown) isreacted along the line o'f'contact Hi -26 and is brought to bear upon "the tops of a multiplicity of the aberrations iii. The motion of abrasive particles on the cutting periphery 3P move transversely of the ab i ns a an a ute a le s 6- Thusno material can be removed from the base circle l 6b of Fig. 3 by the corrective operation show n; Fi nt l t e er ation it are c ml iel emo Determination of the form it? of the lapping wheel it, which will contact the predetermined X el'crc sect n of race 2 nder t Ke e n l re t onsh o he axes of r a on o race and hsel pr nts a sse et al o lem which may be solved in several ways of which the l w n is one: attern when o es tially the diameter and thickness of the lapping wheel 18' but having a relatively soft deformable pl s ic i a f x r mod lin c ay, is oun ed for rotation with its periphery in contact with the race 2 as shown in Fig. 4, ,In this pattern forming operation the respective axes of workpiece and pattern wheel have a relationship which is similar to the corrective abrading step shown by Fig. 4, when work and pattern wheel are rotated in the contact described; the plastic rim of the pattern wheel is deformed to take on a peripheral contour which contacts the work along the line 29-29. From the pattern wheel, having its periphery thus formed, a lapping wheel i3 is made to duplicate the dimensions and contour of the pattern wheel. The lapping-wheel will then likewise contact the groove .3 of race 2 when mounted in the race correcting relationship showninFigJl.

Well known wheel dressing and truing devices operating on the principleofthe pantograph have been used to advantage in preparing the desired peripheral contour on the lapping wheel it by use of the followingsteps: It hasbeen found convenient opticallyproject the image of the.

periphery of the pattern wheel on a plane parallel to the wheel axis and at substantial magnification. From this projection, a template duplicating the thus enlarged image may be made. The tracer element of the pantograph may then be moved with accuracy over the prepared template. This causes the wheel dressing tool, pantograph-ically controlled, to duplicate at reduced scale the template dimensions, thus forming the cutting periphery MP of the lapping wheel in substantial identity to the dimensions and form V of the plastically formed pattern wheel.

Preferably the lapping wheel I8 of the corrective stepof Fig. l is less free cutting than the grinding wheel i2 of Fig. 2. However, though lapping wheels which cut more freely, remove the aberrations L6 more rapidly, they are also more likely to cause smaller but nevertheless undesirable chatter marks to be set up in the race surface along the line of contact 2il-2ll. Lapping timemay, income instances, be conserved if the lapping wheel in the first corrective step ofl' ig. 4 be of'relativelyfree cutting abrasive characteristicsand a second corrective step as shown in Fig. 5 'beapplied to correct any chatter marks (28-429 "of 'Fig'. left by the first corrective "step.

The second corrective step is like unto the first except preferably the lapping wheel 22, which 'may beiorined inithe manner described relative to wheel :8, is of finer or lessfree' cutting abrasive qualities than wheel i8 of Rig-4 and it preferably has its axis of rotation skewed oppositely in an gular relationship tothat'of wheel l8 so that the peripheral-line. of cutting contact between wheel 22 and race-2 lies in-a line 24 -2 "which crosses both lines iii-ill and 20-20 (see Fig.- 6) thus tending toreduceanypreviously existing chatter marks. PreferablyLalsb the lapping wheel is of sufiicientlyL-fine"cutting action that it exerts substantially a polishin action. Any chatter or 1 scratches lefttherebyrbeingiot negligible deleteri- -ous 'efiectwhen followed byHtheneXl; step in the manufacture of the bearing .whichis fullydescribed :in the said United States' Patent No. 1,708,491 and which, therefore, is not repeated here' v it isto'be understood that thepresent description and drawings are illustrative 1 rather than limiting. That -ia'the present process is intended for application "to the ball contacted surfaces of outerraces'fi' as well as to-the inner races shown, subject, of course, to such alterations in wheel diameter andfor m as may be imposed byv the form and dimensions of the surfaces to becorrected. Neither do I intend to'limit V rny process-to use in the manufacture of the-specific type. of ball bearings shown.

I claim as my invention:

1. The process of preparing a ball bearing raceway which includes the steps of generating the ball contacted raceway. surface a's a surface of revolutionsubstantially to its final for'ni and dimensions by rotating the .race about its working axis in fixed positionancl in cutting contact with grinding wheel iioi complemental peripheral form in its axial plane and rotated about its axis while supportegl in fixed position parallelcto the race axis, generating the form oftberieriphery of a deformable pattern wheelby rotating the same, with; its periphery in contact-with theball contacted raceway surface; the race being rotated about its axis in ljxed position and the pattern wheel'being rotatediabout'its axis in fixed position which is. neither co-planarhortiparallelsto the axi of the race, for. the PllfiPD-Seibf forming y a contour on the periphery of said pattern wheel which makes, with the ball contacted race surface, a line of grinding contact at an angle with the line of grinding contact between race and grinding wheel which obtained in the raceway generating step, reproducing the peripheral contour and dimensions of the pattern wheel in an abrasive wheel, reducing any protuberant aberrations from the ball contacted race surface by rotating the abrasive wheel in cutting contact with the rotating race while the axial relation of the race and the abrasive wheel are substantially like the relation which existed therebetween in the pattern forming step, and finishing the raceway surface by running the bearing in the presence of an abradant during a step of finally adjusting the parts thereof into a predetermined relation.

2. The process of preparing a ball bearing raceway which includes the steps of generating the ball contacted raceway surface as a surface of revolution substantially to its final form and dimensions by rotating the race about its Working axis in cutting contact with a grinding wheel of complemental peripheral form in its axial plane and rotated about its axis While supported parallel to the race axis, generating the form of the periphery of a deformable pattern wheel by rotating the same with its periphery in contact with the ball contacted raceway surface the race being rotated about its axis and the pattern Wheel being surface by rotating the abrasive wheel in cutting rotated about its axis which is neither co-planar nor parallel to the axis of the race for the purpose of forming a contour on.the periphery of the pattern wheel which makes, with the ball contacted race surface, a line of grinding contact at an angle with the line of contact between race and grinding wheel which obtained in the raceway generating step, reproducing the peripheral contour and dimensions of the pattern wheel in an abrasive wheel, reducing any protuberant aberrations from the ball contacted race surface by rotating the race about its axis and in cutting contact with an abrasive wheel having its periphery formed substantially in duplication of the periphery generated on the pattern wheel in said pattern forming step and bearing during the present race abrading step an axial relation to the race similar to the relation of race and pattern wheel axes in the said pattern forming step, a second pattern wheel forming step and a second race abrading step performed after the manner of the respective said steps but with an axial relation between race and wheel which differs from that of both the said form grinding and abrading steps, and finishing the raceway surfaces by the method of running the bearing in the presence of an abradant during the step of finally adjusting the parts thereof into a predetermined relation.

3. The process of preparing a ball bearing race which includes the steps of generating the ball contacted raceway surface as a surface of revolution substantially to its final form and dimensions by rotating the race about itsworking axis in cutting contact with a rotating grinding wheel, generating the form of the periphery of a deformable pattern wheel by rotating the same with its periphery in contact with the ball contacted raceway surface the axis of the pattern wheel contact with the rotating race while the relation of the abrasive wheel and the race are substantially like the relation which existed therebetween at the conclusion of the pattern forming step, and finishing the raceway surface by running the bearing in the presence of an abradant during a step of finally adjusting the parts thereof into a predetermined relation.

4. The process of preparing a ball bearing race which includes the steps of generating the ball contacting raceway surface substantially to its final form and dimensions as a surface of revolution by rotating the race about its working axis without movement therealong in cutting contact with a complementarily formed grinding wheel rotated about and prevented from translation along its axis which is located co-planar and parallel to the race axis, generating the complementarily formed periphery of a deformable pattern wheel by rotating the same with its periphery in contact with the ball contacted raceway surface the axes of the pattern wheel and race being neither co-planar nor parallel and having at the end of the pattern forming step no relative movement therebetween, neither race nor pattern wheel having movement along their respective axes during the present step, reproducing the contour and dimensions of the pattern wheel in an abrasive wheel, reducing any protuberant aberrations from the ball contacted race surface by rotating the last described abrasive wheel in cutting contact with the rotating race while the relation between the axes of wheel and race and the position of said wheel and race on their respective axes is substantially lik the relation which existed therebetween at the conclusion of the pattern forming step, and finishing the raceway surface by running the bearing races in assembled relation in the presence of an abradant during a step of finally adjusting the parts thereof into a predetermined relation.

HAROLD N. SEYFERTH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,269,808 Gray et a1. June 18, 1918 1,352,790 Danielsson Sept. 14, 1920 1,708,491 Alden Apr. 9, 1929 1,865,392 Hutchinson et al. June 28, 1932 1,968,550 Barnes a July 31, 1934 2,004,649 Booth et al June 11, 1935 2,073,079 Theler et al. Mar. 9, 1937 2,115,908 Fox May 3, 1938 2,187,471 Hutchinson Jan. 16, 1940 

